This application is related to DE 197 27 652.0 filed on Jun. 30, 1997, which is incorporated by reference in its entirety for all purposes.
The invention relates to a coupling for connecting vacuum-insulated line ends via a coupling socket and a coupling plug which are provided for conveying a cryogenic medium and which have means at the outer line ends that close the line ends.
Couplings for cryogenic media are already known which can be divided into two groups on the basis of their connection mechanism and their means for opening and closing the line ends.
DE 19516029 C1, DE 4041337 A1 and DE 4339676 A1 disclose couplings for cryogenic media which have a coupling plug and a coupling socket. The coupling plug is inserted into the coupling socket so that the outer vacuum-insulated coupling housings overlap and a connection element arranged on the coupling plug can be engaged with a counter-part arranged on the coupling plug. The connection is established by screwing the coupling plug to the coupling socket. During the performed process of sliding the coupling plug into the coupling socket, the coupling is first sealed off against the ambient medium; then the means that close the line ends are opened. The valve-like means in this embodiment of the coupling are located far away from the separation plane inside the coupling socket in the coupling plane.
In the separation plane, the outer faces of the coupling plug and the coupling socket are directly across from each other.
In the coupling plane, the means that close the line ends are directly across from each other. The means can be opened or closed and, when the means are opened, cryogenic medium can flow from the line end of the coupling plug to the line end of the coupling socket.
Moreover, DE 4104711 A1 and U.S. Pat. No. 4,335,747 A1 disclose the technique of sealing against ambient medium separately from the opening/closing of the means directly adjacent to the separation plane by means of ball valves. The connection of the coupling plug with the coupling socket is established with mechanical elements in the separation plane. Likewise far away from the separation plane, in the coupling socket, they have valve-like means whose opening is effectuated by means of the line end of the coupling plug that can be mechanically slid beyond the separation plane and through the opened ball valves. For this purpose, the line end of the coupling plug is configured to be flexible like a corrugated hose.
The valve-like means of the known couplings are located far away from the separation plane in the coupling plane. The maintenance of the couplings, e.g. the replacement of the gaskets, calls for a great deal of assembly work and/or is only possible by destroying parts of the coupling. It entails long down-times for the couplings. The interlocking plug-in/push-in connection of the coupling housing made of stainless steel requires high surface quality and fitting precision as well as high purity of the connection surfaces in order to be able to carry out the joining process with low force. By the same token, the plug-in/push-in connection is unsatisfactory from a safety standpoint when the coupling socket is located as a refueling device (tank closure) on a vehicle and the coupling plug is located on a pump of a service station, since the plug-in connection can cause serious damage to the service station and/or the vehicle if the vehicle drives away while it is still connected, even if the coupling plug is separated form the coupling socket in the separation plane and the coupling plug to the coupling socket is located in the coupling plane. In addition, during the refueling of cryofuel tanks of vehicles, lay persons operate the coupling, which calls for a simple and safe design of the coupling so that the users do not come into contact with the cryogenic fuel.
Therefore, couplings for cryogenic media would be desirable in which the disadvantages according to the state of the art are avoided.
The invention is based on the objective of creating a coupling for cryogenic media that is simple to maintain and whereby the operational safety as well as operating errors are improved in comparison to the prior art couplings.
This objective is achieved according to the invention by a coupling of the type described above having the features of claim 1.
Advantageous embodiments of the invention are described in the dependent claims.
Due to the structure of the coupling according to the invention, the connection of the line ends of the coupling plug and the coupling socket is established directly adjacent to the separation plane, since all of the means for closing the two line ends are provided directly adjacent to the separation plane, so that the separation plane and the coupling plane lie virtually in the same plane. This facilitates the handling of the coupling since plug-in/push-in processes of the stainless-steel coupling housings are eliminated. The safety is increased since, in case of error, no interlocking connection holds the coupling plug in the coupling socket. In addition, all of the gaskets are located detachably directly adjacent to the separation plane and are thus readily accessible. Therefore, the replacement of defective gaskets can be done in a simple manner, since the gaskets are accessible via the line ends. For this purpose, the gasket of the control rod is situated in a recess that is open towards the coupling side and covered by a centering element that can be detached, i.e. screwed, from the outside. The virtually straight-line sliding of the control rod and of the closing element is achieved by the centering element attached to the face of the control rod and that engages with a counterpart situated on the closing element of the coupling socket so as to hold the centering element in an interlocking manner. The interlocking connection ensures the axial guidance of the control rod which is centered in the guided closing element of the coupling socket.
The means that close the two line ends open in the same direction, so that the means can be opened merely by an axial control movement that a control rod executes beyond the separation plane. Here, the control rod provided for the coupling plug has a gasket that is pulled by means of the force of a spring element or of a bellows against a sealing surface formed at the line end, while the gasket of the coupling socket supported by a closing element is pressed by the force of a spring element or bellows against the sealing surface present on the line end. If the control rod slides, for example, axially to the coupling socket due to a extending control unit, the gasket lifts the control rod off of the sealing surface; at the same time, the control rod removes the closing element from the seat against the force of the spring element or the spring properties of the bellows, so that the gasket on the closing element is likewise lifted off of the sealing surface and the cryogenic medium can flow from the coupling plug to the coupling socket.
The sealing of the coupling plug and the coupling socket in the separation plane preferably takes place via two coupling surfaces on each of which there is a gasket. The one outer gasket seals the coupling housing against the penetration of ambient medium and prevents ice formation, whereas the inner gasket seals the means so as to prevent the escape of cryogenic medium. Thanks to the gaskets that form a sealed annular chamber when they are in the coupled state, a direct link between the warm ambient medium with the cryogenic medium is prevented.
The remote control of the coupling according to the invention is achieved by the direct release of the flow path of the cryogenic medium independent of the plug-in/push-in paths via a control unit. The detachable and, in case of emergency, releasable connection of the coupling plug and coupling socket is carried out previously in a separate step. This ensures that the operator of the coupling does not come into contact with the cryogenic medium since he/she only has to establish the connection of the coupling plug and coupling socket at the coupling, and the opening of the means takes place away from the coupling via an operating element. The opening of the means can also be carried out automatically at a prescribed time, e.g. by inserting coins or tokens or by using a credit or debit card.
An especially simple control unit has bellows, preferably metal bellows, whose inner chamber is connected to a control line whose other end is connected to a compressed gas chamber. The control line contains a remote-controlled valve that can be opened or closed via a control signal.
According to another embodiment, the control unit is configured as a piston-cylinder unit.
The dimensions of the coupling can be reduced and the mechanical structure can be greatly simplified if the control unit is located in the line end, since passages and connections are dispensed with and the means can be connected directly to the control unit.
The coupling can be cooled down when the means are closed by means of two lines that are connected to the line end. In this process, the line with the smaller diameter serves as the filling line through which the cryogenic medium flows into the line end and pre-cools the line end. The evaporated medium flows through the line with the larger diameter. When the coupling is in operation, the cryogenic medium flows through both lines in order to be able to achieve the largest possible mass flows and thus a shortening of the filling time with little pressure loss.
The connection of the coupling plug with the coupling socket is established via a locking element that is supported on the coupling plug (fixed bearing) and that pulls the coupling socket against the coupling surfaces with the gaskets. For this purpose, the coupling socket has a flange along its circumference behind which a half-shell element of the locking element grasps and which is pulled to the coupling plug side by means of a rod assembly. In this process, the gaskets tightly seal the coupling surfaces of the coupling plug and the coupling socket. The flow pressure that is established in the line end when the means are open also brings about pressure-proportional sealing forces on the gasket on the side of the coupling plug. Advantageously, the locking element is configured in such a way that it can immediately be detached by an emergency release, preferably immediately after the closing process, so that the coupling plug and the coupling socket are soon freely movable. An embodiment of the emergency release can consist of a rip cord that opens the switch-over lever of the locking element and releases the rod assembly with the half-shell element when a specified tensile force on the coupling is exceeded. Naturally, there are numerous other mechanical, pneumatic, hydraulic electric or magnetic embodiment variants of an emergency release that the person skilled in the art can provide, so that the invention is not limited to this embodiment.
An embodiment of the invention is shown in the drawing and will be described in greater detail below.